1. Field of the Invention
The present invention relates to a powder container for collecting and accumulating powder such as toner, and an image forming apparatus having the powder container, such as a copier, a printer, and a plotter.
2. Description of the Related Art
In an image forming apparatus, such as a copier, toner remaining after transfer on a photosensitive drum or an intermediate transfer belt after a toner image is transferred to a recording medium or an intermediate member is removed by a cleaning mechanism, and is collected in a powder collecting box for collection and storage in a centralized manner.
The powder collecting box of this type includes a toner inlet connected to the cleaning mechanism, a toner conveying unit that conveys toner introduced to the box, and a toner detecting unit that detects a degree of a toner capacity of the box (fill factor).
Upon detection by the detecting unit that the box is completely filled with toner, the powder collecting box is replaced.
In view of improving user convenience, the number of times of replacing the power collecting box is reduced as much as possible. To achieve this, the capacity of the box is desirably increased as much as possible.
However, as has been well known, more downsizing and cost reduction have been seen in the image forming apparatus of this type and, in reality, increasing the size of the box only in view of improving powder collectability is not allowed.
The powder collecting box is often placed by using a so-called dead space, such as a space between a paper feeding unit placed at the bottom of the image forming apparatus and an image forming unit positioned above the paper feeding unit.
An exemplary configuration of the powder collecting box is such that a toner conveying unit is provided in a toner cartridge in a box shape (see, for example, Japanese Patent Application Laid-Open No. H11-002947). In this configuration, an eccentric cam is provided on a shaft of a screw for supplying toner to the outside. With this eccentric cam, a flat plate is caused to reciprocate in a horizontal direction to convey toner with the use of protrusions that are formed integrally with the flat plate and are directed inwardly in a shape of an upward arrow head. Furthermore, the cartridge has also provided therein a configuration for detecting the remaining amount of toner.
On the other hand, as for toner introduced to a developing device for development, it is important to achieve a smooth toner movement to prevent a supply failure. However, some of the accommodated toner may be coagulated to cause a so-called blocking phenomenon, which will inhibit a smooth movement.
To get around this problem, a conventional configuration for loosen toner with such a blocking has been suggested (see, for example, Japanese Patent Application Laid-Open No. H10-207202). In this configuration, in some cases, a plate member that is placed in a developer accommodating unit and is capable of reciprocating is provided, and the plate member is provided with a protruding portion at a toner flow inlet and in the entering toner. By causing the plate member to reciprocate, the protruding portion looses the toner.
However, in view of downsizing, when there is no margin in a height direction of the image forming apparatus body, the dimensional ratio of the powder collecting box inevitably be such that the box is long in a horizontal direction (X and Y directions) and small in a height direction (Z direction). That is, the box shape tends to be a flat shape that is wide in a horizontal direction and low in height.
With such a box shape, it is extremely difficult to evenly accumulate toner, and there is a possibility that the toner may be accumulated as being partially coagulated. If the toner is coagulated near the toner detecting unit, it is detected that the box is filled with toner despite the fact that the entire box is not yet full, and a replacement operation is requested early in a non-full state, thereby leading to deterioration in user convenience.
The technology disclosed in Japanese Patent Application Laid-Open No. H11-002947 is aimed at efficiently supplying toner to the end while preventing coagulation of toner previously accommodated in a cartridge. The conveying direction of the protrusions placed in an upward arrow head is such that, as shown in FIG. 7 of Japanese Patent Application Laid-Open No. H11-002947, the protrusions cause the toner to be unidirectionally headed toward the toner detecting unit through a mutual operation, even though the protrusions cross and differ one another.
Therefore, when this conveying scheme is applied to the powder collecting box, the toner tends to be coagulated near the toner detecting unit, thereby not solving the problem of erroneous detection.
On the other hand, in the technology disclosed in Japanese Patent Application Laid-Open No. H10-207202, the introduced toner is pushed by the reciprocating plate member for movement. However, the introduced toner has the largest amount at an introduction side, and as the toner gradually moves from an introduction inlet, the toner becomes evened in an inner space and the amount to be moved by the plate member is decreased. This may decrease the amount reaching the position of the toner detecting unit. For this reason, in the case where the toner collected in the powder collecting box is deposited in a manner such that the amount of toner is the largest near the introduction inlet and is gradually decreased in the course of reaching the position of the toner detecting unit, if a state occurs such that the movement of toner to be newly introduced to the powder collecting box is inhibited, this state cannot be detected by the toner detecting unit. For example, since a toner-full state cannot be detected, toner will flood near the introduction inlet to pollute an area near a grounding portion of the powder collecting box.
In this manner, if the toner behavior in the powder collecting box is inappropriate, even with provision of the powder detecting unit for detecting a toner-full state, a toner-full state may not be correctly detected by this unit.